Available in both 335mm and 500mm long and fits in the outer frame roller channel which is 19mm deep. 
 
It is "hold-open" and by moving the restrictor laterally in the channel, many angles of opening and "holding" are achievable (from under 90 degrees up to 130 degrees). 
 
There is a friction adjustment by means of a "Phillips" screw. 
 
All materials used are durable and non-corrosive. 
Restrictors are available in 430 Stainless Steel as standard.